Surgeons in operating rooms around the world perform simple and complex surgical procedures with the use of surgical microscopes. Many of these procedures require the use of ultra small micro instruments, devices, and medical supplies. In addition, surgeons conducting these procedures are operating on extremely delicate and microscopic patient anatomy. Many of these operations could not be performed without the use of magnification—or microsurgery. As surgery typically must be conducted in a “sterile field,” and because the surgical microscopes are complex instruments that would be difficult to sterilize effectively for each procedure, microsurgery typically requires that the microscope be covered or “draped” with a sterile, pliable drape. This drape serves as sterile barrier between the microscope and the patient, and protects the sterile field by allowing a surgeon who is wearing sterile surgical gloves and gowns to position the microscope over the patient without contaminating himself or the patient and sterile field. The drape also protects the surgical microscope against contamination via the transfer of bacteria, viruses, and other potentially infectious microbes from a patient to the external surfaces of the microscope. The typical surgical microscope is a costly instrument with a useful life of many years and is routinely used to conduct surgery on thousands of patients, thus making protection against contamination to the patient or patient to the microscope important.
The general shape or pattern of a typical surgical microscope drape is that of a rectangular or otherwise configured flexible sheet of material with extremities designed to fit over the optics of a variety of surgical microscope designs. As the rectangular shape is held up vertically, the top short side of the rectangle is open, the long sides of the rectangle are enclosed, and the bottom short side is enclosed with a fitting for an objective lens housing and transparent non-magnifying lens cover. Prior to sterilization, the drape is systematically folded in such a manner as to allow a person dressed in sterile gloves and gown to pull the open end of the drape over the surgical microscope. The lens cover is then fitted onto the objective lens or front lens of the microscope. Generally, the objective lens points down toward the sterile field and is the component on the microscope that is closest to the patient. Because of the close proximity of the objective lens to the patient and the sterile field, it is the component most likely to act as a conductor and/or transmitter of contamination and/or infection.
The main components of a surgical microscope include the microscope body, which houses the optics; the floor stand, ceiling, or wall mount from which the optics are suspended; and the light source. As the light source is activated, illumination is directed through the objective lens to illuminate the desired subject at a distance that is determined by the focal length (e.g., f=300 mm) or working distance of the objective lens or variable lens system of the microscope body. An image of the illuminated subject is reflected back through the objective lens and is then projected to the eyes of the microscope user via an optical pathway in a system of prisms, mirrors, and lenses in the microscope body, binoculars, and eyepieces.
However, as illuminating light passes through the objective lens, it is not uncommon for some of the light to be reflected by the drape's lens cover, creating glare. This glare may result in the creation of chromatic and spherical aberrations for the user or may block the field-of-view entirely. There have been various attempts at solutions that would resolve this problem but none are completely effective.
An attempted solution pursued by some surgical microscope users is to remove the sterile lens cover that covers the objective lens from the drape. However, this attempted solution allows a non-sterile lens to be close to the sterile field or a patient's open incision. Contamination of a surgeon's instruments is likely if any instrument inadvertently touches the exposed non-sterile objective lens of the microscope. In addition, high-speed drills are often utilized in microsurgery that cause the uncontrolled displacement of bodily fluids or bone chips up towards the unprotected objective lens of the microscope. The clinical and health risks of this attempted solution are evident.
Another attempted solution has been to create a sterile microscope drape with a “dome-shaped” objective lens cover. The purpose of the dome is to reduce refracted light. However, the properties of curvature in this type of design compromise the magnifying performance of the microscope—performance for which microscope manufacturers have strived mightily to achieve and end-users have paid handsomely to acquire. In addition, certain sterilization processes through which some drapes are subjected have been known to leave condensation on the inside of a convex lens as the drape cools down after sterilization. Regardless of whether the dome is convex or concave in nature, neither design completely eliminates chromatic or spherical aberrations or undesirable glare. The result is that users of dome drapes must force their eyes to accommodate aberrations caused by the design. This can expedite and increase eyestrain and fatigue and may even cause headaches in some users. Aside from the optical shortcomings of dome covers, end users of this design continue to complain about unwanted glare or continue to compromise aseptic technique by removing the sterile dome-shaped objective lens cover.
Yet another attempted solution offered by a surgical microscope manufacturer involves removing the sterile lens cover from the drape and installing a sterile slanted lens cover. The slanted lens has proven to be very effective at completely eliminating the unwanted glare described heretofore. However, this methodology produces other undesirable issues: (1) the slanted lens must be sterilized every time it is used. This redundant process is expensive and inconvenient when personnel labor and sterilization costs are calculated, (2) the slanted lens itself is proprietary and is not inexpensive, (3) given the rigors of the operating room environment, a reasonable likelihood exists that the lens may become lost or broken, (4) there is a possibility that the person installing the sterile slanted lens prior to each procedure may become contaminated when interfacing with the non-sterile microscope body.
And finally, an attempted solution has emerged which utilizes a sterile microscope drape that includes a slanted lens cover. The housing of the slanted lens cover is inserted onto the bottom of the microscope objective lens during the microscope draping process and is held in place by friction. However, due to the lens angle necessary to eliminate unwanted glare, the drape of the objective lens housing is excessively tall and presents additional challenges for compact packaging. In addition, sterile microscope drapes currently in use worldwide typically do not utilize a tall objective lens housing but rather a low-profile housing. So the height of this tall slanted lens cover housing reduces the working distance (the distance from the surgical site to the bottom of the objective lens) available to the surgeon. As predetermined and precise working distances are important to surgeons, this proposed solution can be cumbersome and generally is not practical for many types of modern microsurgery. In addition, the requirement for a specialized drape of this sort can present availability and cost problems not present when standard drapes are used.
Accordingly, it can be seen that needs exist for improvements to surgical drapery and/or microscopes to eliminate or at least significantly reduce the glare experienced by microscope users without compromising microscope optical performance, sterility, or surgeon technique. It is to the provision of such a solution that the present invention is primarily directed.